/* Clean, high-contrast theme */
:root {
  --bg: #0b1020;
  --bg-2: #111936;
  --card: #24334a;
  --card-border: #0f1a2c;
  --accent: #34d399;
  --accent-2: #ef4444;
  --match: #16a34a;
  --text: #f8fafc;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", Helvetica, Arial, sans-serif;
  background: radial-gradient(1200px 600px at 50% -200px, var(--bg-2), var(--bg));
  color: var(--text);
  min-height: 100vh;
  display: grid;
  place-items: center;
}

.app { width: 100%; max-width: 980px; padding: 24px; }

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
}

.header h1 { margin: 0; font-weight: 700; letter-spacing: 0.5px; }

.controls { display: flex; align-items: center; gap: 12px; }

button {
  border: none;
  background: var(--accent);
  color: #062217;
  font-weight: 700;
  padding: 10px 14px;
  border-radius: 10px;
  cursor: pointer;
}
button:hover { filter: brightness(1.1); }
button:active { transform: translateY(1px); }

.grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 12px;
}

.card {
  position: relative;
  width: 100%;
  padding-top: 100%; /* square */
  perspective: 600px;
}

.card-inner {
  position: absolute;
  inset: 0;
  border-radius: 12px;
  transform-style: preserve-3d;
  transition: transform 280ms ease;
}

.card.face-up .card-inner { transform: rotateY(180deg); }

.face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: 12px;
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: clamp(20px, 4.2vw, 34px);
}

.face.front { background: var(--card); border: 3px solid var(--card-border); }
.face.back { background: #122039; border: 3px solid var(--card-border); transform: rotateY(180deg); color: #e6f6ff; }

.card.matched .face.back { background: var(--match); border-color: #0f3f22; color: #03220f; }
.card.matched .face.front { opacity: 0.18; }

.card.blank .face.front, .card.blank .face.back { background: transparent; border: 2px dashed #58739a; }
.card.blank { pointer-events: none; }

.footer { margin-top: 18px; opacity: 0.75; }

/* stronger focus ring for accessibility */
.card:focus-visible, button:focus-visible {
  outline: 3px solid #93c5fd; /* sky-300 */
  outline-offset: 2px;
}

/* subtle entry animation */
@keyframes pop {
  from { transform: scale(0.96); opacity: 0; }
  to   { transform: scale(1); opacity: 1; }
}
.card { animation: pop 260ms ease both; }